Power-Module Substrate Brazing Oxide Film Control
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Solution Overview
Problem
The bonding interface between the ceramic substrate and the heat-radiation layer in power-module substrates is prone to separation due to oxide film formation and erosion, especially at the peripheral parts where thermal stress is highest, leading to reduced bonding reliability.
Innovation Solution
A manufacturing method that includes a surface treatment step to reduce the oxide film thickness on the ceramic substrate to 3.2 nm or less at the intended bonding area between the ceramic substrate and the heat-radiation layer, using acids like hydrochloric acid to prevent oxide film erosion and enhance bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ceramic substrate and copper plate are bonded by brazing at high temperature (800-930°C), then the circuit layer bonding is achieved, but an oxide film is formed on the other surface of the ceramic substrate
Solution Approach 1:
The patent applies preliminary action by performing surface treatment (acid washing or plasma treatment) on the ceramic substrate before bonding the heat-radiation layer. This pre-treatment removes or reduces the oxide film formed during the first brazing process, ensuring a clean bonding surface for subsequent aluminum plate bonding and preventing bonding defects.
Solution Approach 2:
The patent converts the harmful oxide film into a beneficial process control indicator. The oxide film formation during high-temperature brazing is not completely prevented but is instead managed through controlled surface treatment processes that selectively remove the oxide layer, transforming the problematic oxidation into a manageable intermediate state that ensures proper bonding conditions.
2Ease of manufacture
If the heat-radiation layer is brazed on the oxidized ceramic substrate, then the bonding process is simplified, but separation occurs at the bonding interface especially at peripheral parts
Solution Approach 1:
The patent performs preliminary surface treatment (acid washing with hydrochloric acid or plasma treatment) on the ceramic substrate before bonding the heat-radiation layer. This pre-treatment removes the oxide film that would otherwise cause separation, ensuring a clean bonding surface while maintaining process simplicity through established surface treatment techniques.
Solution Approach 2:
The patent changes the surface chemistry parameters of the ceramic substrate by controlling oxide film thickness to 3.2 nm or less through acid concentration, treatment time, or plasma power parameters. This parameter control ensures optimal bonding conditions without requiring complete oxide prevention during the first brazing process.
3Ease of manufacture
If flux is used to bond the heat-radiation layer and heat sink, then the bonding is facilitated, but the flux erodes the oxide film at the peripheral part of the bonding interface
Solution Approach 1:
The patent performs preliminary surface treatment to remove or reduce the oxide film before flux application. By pre-cleaning the surface with acid or plasma, the subsequent flux bonding process does not need to aggressively remove oxide material, thereby preventing erosion at the peripheral bonding interface while still facilitating proper bonding.
Solution Approach 2:
The patent applies preliminary anti-action by removing the oxide film that would be eroded by flux through a controlled pre-treatment process. This prevents the harmful erosion effect by eliminating the target material (thick oxide layer) before the flux bonding process begins, while still allowing the flux to perform its beneficial bonding function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively prevents separation at the bonding interface and improves bonding reliability between the ceramic substrate and the heat-radiation layer, even when using flux for brazing, by ensuring a thin oxide film at the peripheral parts.
Implementation Method 1
a surface treatment step after the circuit layer bonding step and before the heat-radiation layer bonding step, in which a thickness of an oxide film on the other surface of the ceramic substrate is made 3.2 nm or less
Implementation Method 2
the ceramic substrate and the copper plate are bonded to each other by brazing material of reactive metal; and the ceramic substrate and the aluminum plate are bonded to each other by Al—Si based brazing material
Data Source
AI summary
A manufacturing method of power-module substrate (10), the power-module substrate (10) being obtained by joining a circuit layer (12) made of copper to one surface of a ceramic substrate (11) and joining a heat-radiation layer (13) made of aluminum to the other surface of the ceramic substrate (11), including: a circuit layer bonding step in which the circuit layer (12) is brazed on the ceramic substrate (11), a surface treatment step after the circuit layer bonding step in which a thickness of an oxide film on the other surface of the ceramic substrate (11) is made 3.2 nm or less at least at a peripheral part of an intended bonding area between the ceramic substrate (11) and the heat-radiation layer (13), and a heat-radiation layer bonding step in which the heat-radiation layer (13) is brazed on the other surface of the ceramic substrate (11) after the surface treatment step.